scholarly journals Balanced and Radiating Wave Responses to Diurnal Heating in Tropical Cyclone–Like Vortices Using a Linear Nonhydrostatic Model

2019 ◽  
Vol 76 (8) ◽  
pp. 2575-2597 ◽  
Author(s):  
Rebecca C. Evans ◽  
David S. Nolan
Keyword(s):  
High Frequency ◽  
Diabatic Heating ◽  
Inner Core ◽  
Vertical Motion ◽  
Radiative Heating ◽  
Convective Heating ◽  
Direct Response ◽  
Frequency Responses ◽  
Nonhydrostatic Model ◽  
High Frequency Waves

Abstract The diurnal cycle (DC) in the cirrus canopy of tropical cyclones (TCs) is a well-documented phenomenon. While early studies linked the DC in the area of the cirrus canopy to a DC in the strength of eyewall convection, later studies considered it a direct response to the DC of radiation in the cirrus canopy. In this study, an idealized linear model is used to examine the extent to which linear dynamics can capture the DC in TCs, in particular the transition between balanced and radiating responses to diurnal heating. The model heat forcing is physically motivated by the diabatic heating output from a realistic simulation, which illustrates the presence of a DC in moist convective heating and radiative heating in the eyewall, and a DC in radiative heating in the cirrus canopy. This study finds that the DCs of heating in the eyewall yield a response that is restricted to inside the RMW by the high inertial stability in the inner core. The DC of radiative heating in the cirrus canopy yields a response throughout the entire cyclone. Lower-frequency responses, of diurnal and semidiurnal frequency, are balanced throughout much of the cyclone. High-frequency waves with periods under 8 h, created at sunrise and sunset, can radiate outward and downward. These results indicate that diurnal responses are balanced in the majority of a TC and originate in the cirrus canopy, instead of the eyewall. The DC in cirrus canopy vertical motion also appears to originate in the cirrus canopy.

scholarly journals On the spectrum of vertically propagating gravity waves generated by a transient heat source

2004 ◽  
Vol 4 (1) ◽  
pp. 1063-1090 ◽  
Author(s):  
M. J. Alexander ◽  
J. R. Holton
Keyword(s):  
Heat Source ◽  
Gravity Waves ◽  
High Frequency ◽  
Convective Heating ◽  
Frequency Spectra ◽  
Wide Range ◽  
Frequency Components ◽  
High Frequency Waves ◽  
Vertically Propagating ◽  
Group Velocities

Abstract. It is commonly believed that cumulus convection preferentially generates gravity waves with tropospheric vertical wavelengths approximately twice the depth of the convective heating. Individual cumulonimbus, however, act as short term transient heat sources (duration 10 to 30 min). Gravity waves generated by such sources have broad frequency spectra and a wide range of vertical scales. The high-frequency components tend to have vertical wavelengths much greater than twice the depth of the heating. Such waves have large vertical group velocities, and are only observed for a short duration and at short horizontal distances from the convective source. At longer times and longer distances from the source the dominant wave components have short vertical wavelengths and much slower group velocities, and thus are more likely to be observed even though their contribution to the momentum flux in the upper stratosphere and mesosphere may be less than that of the high frequency waves. These properties of convectively generated waves are illustrated by a linear numerical model for the wave response to a specified transient heat source. The wave characteristics are documented through Fourier and Wavelet analysis, and implications for observing systems are discussed.

scholarly journals On the spectrum of vertically propagating gravity waves generated by a transient heat source

2004 ◽  
Vol 4 (4) ◽  
pp. 923-932 ◽  
Author(s):  
M. J. Alexander ◽  
J. R. Holton
Keyword(s):  
Heat Source ◽  
Gravity Waves ◽  
High Frequency ◽  
Convective Heating ◽  
Frequency Spectra ◽  
Wide Range ◽  
Frequency Components ◽  
High Frequency Waves ◽  
Vertically Propagating ◽  
Group Velocities

Abstract. It is commonly believed that cumulus convection preferentially generates gravity waves with tropospheric vertical wavelengths approximately twice the depth of the convective heating. Individual cumulonimbus, however, act as short term transient heat sources (duration 10 to 30min). Gravity waves generated by such sources have broad frequency spectra and a wide range of vertical scales. The high-frequency components tend to have vertical wavelengths much greater than twice the depth of the heating. Such waves have large vertical group velocities, and are only observed for a short duration and at short horizontal distances from the convective source. At longer times and longer distances from the source the dominant wave components have short vertical wavelengths and much slower group velocities, and thus are more likely to be observed even though their contribution to the momentum flux in the upper stratosphere and mesosphere may be less than that of the high frequency waves. These properties of convectively generated waves are illustrated by a linear numerical model for the wave response to a specified transient heat source. The wave characteristics are documented through Fourier and Wavelet analysis, and implications for observing systems are discussed.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

First VIKING results: high frequency waves

1988 ◽  
Vol 37 (3) ◽  
pp. 469-474 ◽  
Author(s):  
A Bahnsen ◽  
M Jespersen ◽  
E Ungstrup ◽  
R Pottelette ◽  
M Malingre ◽  
...  
Keyword(s):  
High Frequency ◽  
High Frequency Waves

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

scholarly journals Systematic Variation in Wintertime Precipitation in East Asia by MJO-Induced Extratropical Vertical Motion

2008 ◽  
Vol 21 (4) ◽  
pp. 788-801 ◽  
Author(s):  
Jee-Hoon Jeong ◽  
Baek-Min Kim ◽  
Chang-Hoi Ho ◽  
Yeon-Hee Noh
Keyword(s):  
East Asia ◽  
Large Scale ◽  
Diabatic Heating ◽  
Daily Precipitation ◽  
Lower Troposphere ◽  
Vertical Motion ◽  
Mean Value ◽  
Asian Countries ◽  
The Indian Ocean ◽  
Omega Equation

Abstract The variations in the wintertime precipitation over East Asia and the related large-scale circulation associated with the Madden–Julian oscillation (MJO) are examined. By analyzing the observed daily precipitation for the period 1974–2000, it is found that the MJO significantly modulates the distribution of precipitation over four East Asian countries; the precipitation rate difference between wet and dry periods over East Asia, when the centers of MJO convective activities are located over the Indian Ocean and western Pacific, respectively, reaches 3–4 mm day−1, which corresponds to the climatological winter-mean value. Composite analysis with respect to the MJO suggests that the MJO–precipitation relation is mostly explained by the strong vertical motion anomalies near an entrance region of the East Asia upper-tropospheric jet and moisture supply in the lower troposphere. To elucidate different dynamic origins of the vertical motion generated by the MJO, diagnostic analysis of a generalized omega equation is adopted. It is revealed that about half of the vertical motion anomalies in East Asia are induced by the quasigeostrophic forcings by the MJO, while diabatic heating forcings explain a very small fraction, less than 10% of total anomalies.

The Intensity- and Size-Dependent Response of Tropical Cyclones to Increasing Vertical Wind Shear

2021 ◽  
Author(s):  
Peter M. Finocchio ◽  
Rosimar Rios-Berrios
Keyword(s):  
Wind Field ◽  
Wind Shear ◽  
Diabatic Heating ◽  
Inner Core ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Vertical Coupling ◽  
Tangential Wind

AbstractThis study describes a set of idealized simulations in which westerly vertical wind shear increases from 3 to 15 m s−1 at different stages in the lifecycle of an intensifying tropical cyclone (TC). The TC response to increasing shear depends on the intensity and size of the TC’s tangential wind field when shear starts to increase. For a weak tropical storm, increasing shear decouples the vortex and prevents intensification. For Category 1 and stronger storms, increasing shear causes a period of weakening during which vortex tilt increases by 10–30 km before the TCs reach a near-steady Category 1–3 intensity at the end of the simulations. TCs exposed to increasing shear during or just after rapid intensification tend to weaken the most. Backward trajectories reveal a lateral ventilation pathway between 8–11 km altitude that is capable of reducing equivalent potential temperature in the inner core of these TCs by nearly 2°C. In addition, these TCs exhibit large reductions in diabatic heating inside the radius of maximum winds (RMW) and lower-entropy air parcels entering downshear updrafts from the boundary layer, which further contributes to their substantial weakening. The TCs exposed to increasing shear after rapid intensification and an expansion of the outer wind field reach the strongest near-steady intensity long after the shear increases because of strong vertical coupling that prevents the development of large vortex tilt, resistance to lateral ventilation through a deep layer of the middle troposphere, and robust diabatic heating within the RMW.

Warm Cores, Eyewall Slopes, and Intensities of Tropical Cyclones Simulated by a 7-km-Mesh Global Nonhydrostatic Model

2016 ◽  
Vol 73 (11) ◽  
pp. 4289-4309 ◽  
Author(s):  
Tomoki Ohno ◽  
Masaki Satoh ◽  
Yohei Yamada
Keyword(s):  
Tropical Cyclones ◽  
Inner Core ◽  
Grid Spacing ◽  
Satellite Measurements ◽  
Warm Core ◽  
Nonhydrostatic Model ◽  
Proposed Model ◽  
Tangential Wind ◽  
Balanced Model ◽  
Horizontal Grid

Abstract Based on the data of a 1-yr simulation by a global nonhydrostatic model with 7-km horizontal grid spacing, the relationships among warm-core structures, eyewall slopes, and the intensities of tropical cyclones (TCs) were investigated. The results showed that stronger TCs generally have warm-core maxima at higher levels as their intensities increase. It was also found that the height of a warm-core maximum ascends (descends) as the TC intensifies (decays). To clarify how the height and amplitude of warm-core maxima are related to TC intensity, the vortex structures of TCs were investigated. By gradually introducing simplifications of the thermal wind balance, it was established that warm-core structures can be reconstructed using only the tangential wind field within the inner-core region and the ambient temperature profile. A relationship between TC intensity and eyewall slope was investigated by introducing a parameter that characterizes the shape of eyewalls and can be evaluated from satellite measurements. The authors found that the eyewall slope becomes steeper (shallower) as the TC intensity increases (decreases). Based on a balanced model, the authors proposed a relationship between TC intensity and eyewall slope. The result of the proposed model is consistent with that of the analysis using the simulation data. Furthermore, for sufficiently strong TCs, the authors found that the height of the warm-core maximum increases as the slope becomes steeper, which is consistent with previous observational studies. These results suggest that eyewall slopes can be used to diagnose the intensities and structures of TCs.

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